Whitelist ext-color-buffer-float conformance test

Remove the it from the expectation.

Bug: 640389
Change-Id: Id90ed5c40069fe36710782fe440b385a2b1e69e3
Reviewed-on: https://chromium-review.googlesource.com/1174102Reviewed-by: Kenneth Russell <kbr@chromium.org>
Commit-Queue: Jie A Chen <jie.a.chen@intel.com>
Cr-Commit-Position: refs/heads/master@{#585416}

content/test/gpu/gpu_tests/webgl2_conformance_expectations.py

@@ -968,9 +968,6 @@ class WebGL2ConformanceExpectations(WebGLConformanceExpectations):
         ['linux', ('nvidia', 0x1cb3), 'opengl'], bug=703779)
 
     # Linux Intel
-    self.Fail('conformance2/extensions/ext-color-buffer-float.html',
-        ['linux', 'intel'], bug=640389)
-
     # See https://bugs.freedesktop.org/show_bug.cgi?id=94477
     self.Skip('conformance/glsl/bugs/temp-expressions-should-not-crash.html',
         ['linux', 'intel'], bug=540543)  # GPU timeout